Keratin polypeptides extracted from cultivated human foreskin keratinocytes and from human foreskin epithelium will be separated on slab polyacrylamide gels by electrophoresis. These individual polypeptides will be excised from the gels, exposed to 125 iodine using chloramine T technique described by John Elder, et al, J. Biol. Chem., 252:6510, 1977. These individual iodinated polypeptides will then be subjected to partial trypsin hydrolyses and separated on two dimensional gels. The first dimension being electrophoresis, the second dimension being thin layer chromatography. The purpose of these experiments is to determine the relatedness of the keratin polypeptides. Both extracted from within a single tissue and also to compare the polypeptides extracted from various tissues of a single animal such as esophagus, cervix, epidermis.